how to display system date in all my screens of the project that i developed using yii.Do i have to use model for this?

I think you need to be a lot more specific.

If you just want to display the date on each Html page viewable in your web project (I’m assuming that is what it is), then you could just add some PHP code for the date into your //layouts/main.php view, or even better you could use Yii::app()->dateFormatter->format(‘Y-M-D’, time()) to have it localized.